Added AssemblyInformationalVersion support

Added support for using AssemblyInformationalVersion  assembly_informational_version - we use this for creating pre-release nuget builds (it uses this attribute because it can handle SemVer 1.0.0-pre style versions).

I tried working around this just using a custom attribute at first, but it adds duplicates (we read the same file in that we write, updating certain fields), so added proper support for it.